Three-dimensional asset tracking using radio frequency-enabled nodes

ABSTRACT

Described examples include light fixtures and/or radio frequency (RF) nodes located in a service volume provided with a mobile asset detection system. The RF nodes receive beacon signals transmitted by mobile assets within the service volume. The mobile asset detection system includes a processor, a transceiver and multi-element antenna array. The multi-element antenna array includes multiple discrete antenna elements that, in some examples, are arranged so that at least one of the discrete antenna elements is non-coplanar with the other discrete antenna elements of the antenna array. Using signal attribute values determined from a signal received via each of the respective discrete antenna elements, a three dimensional estimate of the location of the mobile assets in a service volume may be determined.

TECHNICAL FIELD

The disclosed subject matter relates to improvements in determining alocation of a mobile asset in three-dimensions.

BACKGROUND

Positions of asset tags, such as radio frequency identification (RFID)tags, may be tracked using a number of different technologies, such asRFID, global positioning system (GPS), or other radio frequency systems,such as cellular telephone communication. However, these systems maylack range, be subject to interference, or may be overly complex toimplement and maintain, or may rely on third party providers of theparticular communication services, such as a cellular provider. Inaddition, depending upon the service area, known position determiningtechniques may lack accuracy, and may not provide additionalinformation, such as an identifier of the asset tag.

Estimates of an asset tag's position in an extended (e.g., urban-scale)service area may be determined using existing technologies. However, theposition estimates lack accuracy and may be unsuitable for real-timethree dimensional tracking throughout a three-dimensional servicevolume. As mentioned above, three-dimensional positions of a device maybe determined using a number of technologies, such as GPS, but suchtechnology has drawbacks, such as the hardware for suchposition-determining systems is relatively complex and is limited withregard to providing location determination functionality. For example,GPS and other positioning technology does not provide for theassociation of unique identities with the location information, norprovide for reporting of tag positions to a distant or centralcomputational capability, nor provide a tracking function that enablesdevices to be monitored throughout a service volume. In addition, GPSsignals may be occluded by structures in an urban environment.

SUMMARY

Therefore, there is a need for systems and methods for tracking uniquelyidentified mobile assets throughout an extended three-dimensionalservice volume. The concepts disclosed herein provide improvedcapabilities of RF nodes integrated with light fixtures for use inlocation estimation of mobile assets in three dimensions. A network ofRF nodes enables a combination of asset-location data from multiplenodes in order to track asset movement through the space served by theRF node network and to disambiguate and/or improve the accuracy ofthree-dimensional asset-location estimates.

An example of a method relates to a mobile asset detection system inwhich a mobile asset detection device may be coupled to a respectivelight fixture among multiple light fixtures distributed in a servicevolume. The mobile asset detection device includes an antenna arrayhaving multiple discrete antenna elements. The method includes receivinga radio frequency beacon signal emitted from a mobile asset by a mobileasset detection device. Based on outputs of the mobile asset detectionsystem generated in response to the received radio frequency beaconsignal, a value of a signal attribute of the radio frequency beaconsignal as received via each discrete antenna element of the antennaarray coupled to the respective light fixture may be determined. Asignal attribute value is determined for each of the discrete antennaelement. A processor may determine differences between the determinedvalues of the signal attribute of the radio frequency beacon signalreceived via the discrete antenna element. The determined differencesmay be processed to estimate a three-dimensional location of the mobileasset with respect to the mobile asset detection system for a time whenthe mobile asset transmitted the radio frequency beacon signal.

A system example may include a number of radio frequency-enabled mobileasset detection devices configured to detect signals transmitted by aradio frequency-enabled mobile asset within a service volume. The radiofrequency-enabled mobile asset detection devices are distributed withinthe service volume. Each radio frequency-enabled mobile asset detectiondevice may include an antenna array having multiple discrete antennaelements, a detection processor, and a detection transceiver. The systemmay include a fog gateway. The fog gateway includes a fog gateway radiofrequency transceiver communicatively coupled to the number of mobileasset detection devices. The detection processor in each radiofrequency-enabled mobile asset detection device may be configured toreceive via each discrete antenna element of the antenna array a beaconsignal transmitted by the mobile asset, the beacon signal including aunique identifier of the mobile asset. A value of a signal attribute ofthe beacon signal received via each discrete antenna element of theantenna array may be determined. Information related to the uniqueidentifier of the mobile asset and information related to the determinedvalues of the signal attribute may be forwarded to the fog gateway radiofrequency transceiver. At least one processor may be coupled tocommunicate through the fog gateway radio frequency transceiver, and maybe configured to obtain a three-dimensional estimate of a locationwithin the service volume of the mobile asset, based on the forwardedinformation that indicated by the unique identifier of the mobile asset.

A light fixture-based mobile asset detection system example includes anumber of light fixtures, a number of radio frequency-enabled nodes anda fog gateway. The light fixtures may be distributed in a servicevolume, and each light fixture may include a light source forilluminating a portion of the service volume. The radiofrequency-enabled nodes are communicatively coupled in a network. Eachradio frequency-enabled node is coupled to a multi-element antenna arrayhaving multiple discrete antenna elements configured to receive a signalemitted by a mobile asset within the service volume, and collocated witha respective light fixture of the number of light fixtures. Each radiofrequency-enabled node is configured to detect the mobile asset within aservice volume based on receiving a signal emitted by a mobile asset.The received signal is processed to determine a value related to anattribute of the received signal for each of the respective discreteantenna elements. Each radio frequency-enabled node is configuredgenerate information for a three dimensional location estimation basedon the determined values related to the received signal attribute asreceived by the discrete antenna elements, and output a signalcontaining the information for the three dimensional locationestimation. The fog gateway may be communicatively coupled to theplurality of radio frequency-enabled nodes and the plurality of lightfixtures. The fog gateway may be configured to control the lightfixtures and receive signals containing the information for threedimensional location estimation from the radio frequency-enabled nodes.

A light fixture example includes a general illumination light source, anantenna array having multiple discrete antenna elements, a wirelesstransceiver, a memory, a processor and program instructions stored inthe memory. The processor may be coupled to the transceiver and thememory. The execution of the program instructions configures the lightfixture to detect a mobile asset within a service volume in response toreceiving a signal emitted by a mobile asset. The light fixture is alsoconfigured to determine a value related to the emitted signal asreceived via each of the multiple discrete antenna elements, and outputdata based on the determined value related to the emitted signal asreceived via each of the multiple discrete antenna elements.

Additional objects, advantages and novel features of the examples willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing and the accompanying drawings or may be learned by productionor operation of the examples. The objects and advantages of the presentsubject matter may be realized and attained by means of themethodologies, instrumentalities and combinations particularly pointedout in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures depict one or more implementations in accordance with thepresent teachings by way of example only, not by way of limitation. Inthe figures, like reference numbers refer to the same or similarelements.

FIG. 1 illustrates an example of a system architecture for providing thethree-dimensional asset tracking functionality in a hypothetical servicevolume shown from overhead.

FIG. 2 shows a partial cross-sectional view depicting thethree-dimensional nature of the service volume in the systemarchitecture example of FIG. 1.

FIG. 3 is a simplified, functional block diagram of an example of alight fixture or other type lighting device, with at least one wirelesstransceiver and a multi-element antenna array.

FIG. 4 is a simplified, functional block diagram of an example of adriver, providing a data bus, as may be used in the example lightfixture of FIG. 3.

FIG. 5 and FIG. 6 are simplified, functional block diagrams of twoexamples of transceivers that may be used in the example light fixtureof FIG. 3.

FIG. 7 is a simplified, functional block diagram of an example of asystem of lighting fixtures and other equipment, where at least severalof the light fixtures may be similar to the example light fixture ofFIG. 3.

FIG. 8 is a simplified, functional block diagram of an example of ahardware platform for a fog gateway, as may be used in the examplesystems of FIGS. 1 and 7.

FIG. 9 illustrates an example of an estimation of the bearing of asignal source using two antenna elements in a plane.

FIG. 10 shows an example of a disambiguation of a two-dimensionalbearing using three antennas in a plane.

FIG. 11 illustrates an example of a relationship of a signal source in3-dimensional space to an antenna array for use in providing athree-dimensional estimation of a location of the signal source, such asa mobile asset described in the examples of FIGS. 1, 2 and 7.

FIG. 12 is a flowchart depicting an example of a process flow forperforming a three-dimensional location estimation.

FIG. 13 shows an example of an asset tracking tag configured tocommunicate with a system of network of RF-enabled wirelesscommunication nodes.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent that the presentteachings may be practiced without such details. In other instances,well-known methods, procedures, and/or components have been described ata relatively high level, without detailed comment in order to avoidunnecessarily obscuring aspects of the present teachings.

The term “lighting device” as used herein is intended to encompassessentially any type of device that processes, generates, or supplieslight, for example, for general illumination of a space intended for useof or occupancy or observation, typically by a living organism that cantake advantage of or be affected in some desired manner by the lightemitted from the device. However, a lighting device may provide lightfor use by automated equipment, such as sensors/monitors, robots, etc.that may occupy or observe the illuminated space, instead of or inaddition to light provided for an organism. It is also possible that oneor more lighting devices in or on a particular premises have otherlighting purposes, such as signage for an entrance or to indicate anexit. Of course, the lighting devices may be configured for still otherpurposes, e.g. to benefit human or non-human organisms or to repel oreven impair certain organisms or individuals. In most examples, thelighting device(s) illuminate a space or area of a premises to a leveluseful for a human in or passing through the space, e.g. regularillumination of a room or corridor in a building or of an outdoor spacesuch as a street, sidewalk, parking lot or performance venue. The actualsource of light in or supplying the light for a lighting device may beany type of light emitting, collecting or directing arrangement. Wherethe source is driven by electrical power, the light source typicallywill be in a lamp, light fixture or other luminaire. Other elements ofthe device, such as the processor and transceivers of an intelligentlighting device, may be part of the luminaire that contains the lightsource or may be implemented somewhat separately and coupled to operatethe light source in the luminaire.

The term “mobile asset” may be a device, such as an automobile, aground-based robotic device, a bus, an unmanned aerial vehicle, a user'smobile device, or that like that itself includes a radio frequencytransmitter that can operate as an RF asset tag, or a mobile asset maybe a box or the like on a shelf in a warehouse, a wheelchair, cart orsome other movable/portable object having a radio frequency-enabledasset tracking tag coupled thereto. An “asset tag” or “asset trackingtag” may be any device capable of (a) detecting RF node signals and/or(b) emitting signals detectable by RF nodes, e.g. for locationestimation and/or tracking purposes. For ease of further discussion, thefollowing description often uses the term asset tag to encompass aspecial purpose wireless device coupled to an object as well as the RFequipment included in a vehicle, mobile device or the like.

A “node service volume” may be, for example, the volume within which agiven RF node may reliably interact with a radio frequency mobile asset(e.g. within which greater than 50% of RF communications from a tag maybe received). In an example, the service volume is the total volumewithin which the one or more RF nodes in the network can interact with awireless asset tag.

Reference now is made in detail to the examples illustrated in theaccompanying drawings and discussed below.

The use of multi-element antenna arrays in the RF enable network nodesand attendant processing of attribute values determined from an assettag signal received through multiple antenna elements facilitatesthree-dimensional location estimation with improved accuracy. Anadvantage of the disclosed system is the capability to track uniquelyidentified mobile assets in three-dimensions throughout an extendedoutdoor and/or indoor service spatial volume. Different classes ofassets may be tracked and distinguished (e.g., car fleets, drone fleets,drone or car fleets separated by client or functional sub-class). Assetbehavior can in various examples be characterized, flagged, and directed(e.g., in response to time, weather, traffic, emergencies). Variousanalytics may also be derived from asset behaviors. In some examples,location modalities other than or additional to RF node signaling (e.g.,optical signaling, GPS) provide asset location data that may becollected through the network and/or ancillary communicationscapabilities (e.g., the cell network).

FIG. 1 illustrates an example of a system architecture for providing thethree-dimensional asset tracking functionality in a hypothetical servicevolume as shown from overhead. The architecture of the system 100 shownin FIG. 1 includes a number of radio-frequency (RF) nodes 110 a, anumber of edge gateways 110, and a fog gateway 193 that communicate withone another to support location estimation and tracking services formobile assets within the service volume 120. The RF nodes 110 a may beconfigured in a network with the number of edge gateways 110. The numberof edge gateways 110 may be less than the number of RF nodes 110 a.Although shown separately, the functionalities of the edge gateways 110maybe incorporated into a subset of the RF nodes 110 a. The fog gateway193 may communicate through a secondary network 195 (e.g., the Internet)with a computational back end, such as a mobile asset tracking servicer196, a backend server 197, or both.

The RF nodes 110 a and the edge gateways 110 in the example are locatedwithin the service volume 120. The RF nodes 110 a may be configured todetect radio frequency beacon signals transmitted via a node/assetwireless link, such as shown at 189, by the radio frequency-enabledmobile asset 125 when operating within service volume 120. Examples of amobile asset 125 include unmanned aerial vehicles or drones,automobiles, or the like. In addition, an asset tracking tag 126 that islocatable by the system 100 may be coupled to movable objects andpersons 124 thereby enabling the person or object with the tag 126 to belocated and/or tracked. An object or person 124 coupled to an assettracking tag 126 may also be referred to as a mobile asset.

In the illustrated example of FIG. 1, the operational extent of theservice volume 120 may be indicated by the perimeter 123, and mayinclude a coverage obstacle 121, such as building or a source of radiofrequency interference, and an exclusion zone 144, such as an airport orother restricted area (e.g. government complex, protected wildlifehabitat or the like) as well as other features within the perimeter 123.The coverage obstacle 121 may, for example, be a tall building that mayblock or attenuate RF signals 188 between a given RF node 110 a-1 andmobile assets, such as mobile asset 125, on the side of the buildingopposite the given RF node 110 a-1. The exclusion zone 144 may have asecurity perimeter 145. The service volume 120 within the perimeter 123may be an airport, an urban area, a suburban area, a nature preserve, ora large indoor space.

The mobile assets 124, 125 may be configured to transmit an RF signal ina first frequency band that is receivable by one or more of the RF nodes110 a. The mobile asset location estimation and mobile asset trackingfunctions may use, for example, Bluetooth Low Energy (BLE) or otherradio-frequency (RF) protocols. For example, the transceivers in thesystem 100 may operate in one or more frequency ranges, such as the850-900 MHz range, 2.4. MHz, 5.8 MHz or the like. In another example,the RF nodes 110 a may be mounted separately within service zone 120 ormay be collocated with light fixtures (e.g., traffic light,streetlights, stadium lighting, airport obstruction lights or the like)within a service zone 120 in which the system 100 provide supportslocation estimation and/or mobile asset tracking service.

In an example, the physical locations of the RF nodes 110 a within theservice volume 120 are known to a computational capable device (e.g.,edge gateway 100, fog gateway 193, mobile asset tracking server 196, orbackend server 197) of the system 100, and these known physicallocations may be used by the system 100 to derive locations for mobileassets 125 (e.g., asset tracking tags 126 borne by cars, drones, cellphones, packages, persons or other assets or devices that have RFcapabilities installed by original equipment manufacturers, such ascars, drones, cell phones or the like) that receive or exchange signalswith the RF nodes 110 a. For example, the physical locations of the RFnodes 110 a within the service volume 120 may be stored in a memory,such as the fog database (DB) 194 that is coupled to the fog gateway193. Alternatively or in addition, the physical locations of the RFnodes 110 a within the service volume 120 may be stored in a memory ordatabase associated with the network 195, the mobile asset trackingserver 196 or the backend server 197.

The network of RF nodes 110 a (e.g., BLE transceivers integrated withlight fixtures) of system 100 may be a deployed over the service volume120 to provide radio frequency coverage within the service volume 120.The RF nodes 110 a may communicate wirelessly with each other, forexample, via inter-nodal wireless links 127 in a topologically connectednetwork. The RF nodes 110 a may be deployed in an approximately groundsurface-following manner over the service volume 120 but the servicevolume 120 may be extended vertically to an extent as described withreference to FIG. 2.

In some examples, the RF nodes 110 a may be distributed throughout theservice volume 120 in a manner to provide service even where some RFnodes 110 a may have attenuated or limited signal transmission range ina particular direction. One or more of the RF nodes 110 a maycommunicate with an edge gateway 110. The edge gateway 110 may, viacommunication with the fog gateway 193, enable information to beexchanged between the network of RF nodes 110 a and a server, such asmobile asset tracking server 196 or back end server 197. The fog gateway193 and the server typically communicate via a network 195 such as theInternet. Information sent to the network through the gateway caninclude, for example, firmware updates, RF node configurationparameters, and ID updates for asset tracking tags. Information uploadedthrough the gateway can include, for example, tag location data and RFnode performance data. Depending on which device processor will performvarious data processing steps to generate a location estimation relatedto a particular tag or asset, data communications through the gatewaysand network(s) may involve transmissions of signal attribute values orrelated information (e.g. difference values) and/or asset tagidentifiers or related information.

FIG. 2 is a partial vertical cross-section view depicting thethree-dimensional nature of a service volume, such as 120 of example ofFIG. 1. In some examples, the network of RF nodes 110 a may betopologically disconnected sub-networks that communicate via localgateway devices, such as edge gateways 110, with the larger network (ofRF nodes 110 a) or directly with a computational device, such as foggateway 193, or a computational back end, such as the mobile assettracking server 196, or the back end server 197. The network of RF nodes110 a may include both stationary nodes shown by the pentagons in FIG. 1and mobile (e.g., drone-borne) nodes.

As mentioned above, the service volume 120 may extend vertically abovethe respective RF nodes 110 a, edge gateways 110, coverage obstacle 121,exclusion zone 144 and other structures within the service volume 120.FIG. 2 shows a partial vertical cross-section to depict athree-dimensional nature of service volume in the system architectureexample of FIG. 1.

The system 200 of FIG. 2 may be implemented within a service volume 211.The service volume 211 may include indoor volumes (e.g. shopping malls,parking garages, warehouses, big-box, retail stores, tunnels or thelike); outdoor volumes, e.g., a parking lot, a shipping holding area, anairport, an urban area and the space above the urban area (e.g. citystreets, city parks and the like); or the like up to some definedservice volume ceiling (i.e. height above ground or altitude) 299. Forexample, the service volume 211 may be limited to a ground area thatapproximately corresponds to the perimeter 123 of the service volume 120of FIG. 1, and the service volume ceiling 299 may be limited by thereceive power capabilities and/or antenna configuration of therespective RF nodes 210.

As shown in FIG. 2, each RF node 210 may have an approximately sphericalradiation pattern (shown as node service volume 229) enabling arespective node 210 to send and receive signals from tags in theapproximately spherical node service volume 299. The network of RF nodes210 can thus communicate with mobile assets 225 a, 225 b and 225 c(generally, referred to as 225) including tags throughout thethree-dimensional service volume 211. The extent of the service volume211 may be limited by the locations of RF nodes 201 and the respectivenode service volume 229 of each of respective RF node 210. Therespective node service volumes 229 preferably overlap so that two ormore nodes RF 210 can interact with a mobile asset at most points in theservice volume 211 of the system 200.

Of course, each ideally spherical node service volume 229 for eachrespective node 210 may be, in practice, modified by the physicalenvironment in which a respective RF node 210 is located. A node servicevolume 229 may include signal-blocked structural features (e.g., parkinggarages, tunnels, store interiors, RF shielding materials (intentionalor unintentional), or the like). For example, a tall building (i.e. suchas coverage obstacle 121 of FIG. 1) may block RF signals between a givenRF node 210 and mobile assets on the side of the building opposite thegiven RF node within the service volume 211.

In addition, as shown in and described in the discussion of FIG. 1, theservice volume 211 may also have zones of special concern that aredefined within the service volume 211, such as the exclusion zones 144of FIG. 1. In an example of three-dimensional zoning, ground vehiclesand airborne drones may be excluded from an exclusion zone, such as 144of FIG.1. The approach of a mobile asset, such as 225, to within acertain distance of the exclusion zone may produce a warning and/orrequest for corrective action. For example with reference to FIGS. 1 and2, the airborne mobile asset 225 a may move to a location at or in closeproximity to the security perimeter 145 of the exclusion zone 144, andin response, a warning message may be transmitted to the mobile assetfor delivery to the asset operator warning of the mobile asset'sproximity to the exclusion zone. The warning message may include arequest for the mobile asset to change course away from the exclusionzone 144. The warning message may, for example, be produced by acomputing device, such as the fog gateway 193, mobile asset trackingserver 196 and the back end server 197 of FIG. 1, or the like. Forexample, response logic executed in the computing device can respond ina staged manner based on criteria including concentric spatial zones,device class, asset path and speed, state of alert, time of day,weather, and other. In an example of a three-dimensional exclusion zone,aerial drone mobile assets may be warned when flying below a certainaltitude over sidewalks and other rights of way. In an example of adynamically changing exclusion zone, mobile assets are warned of theapproach of an emergency vehicle and directed out of its path.

It may be helpful to describe the respective individual component partsthat may form the systems 100 and 200 described above with respect toFIGS. 1 and 2.

FIG. 3 illustrates a lighting device 10, such as a light fixture or thelike, that includes a light source and one or two wireless transceivers.The lighting device 10 may be used as an RF node, such as RF nodes 110a, and be installed within a light fixture located within a system, suchas 100 or 200.

The emitter or emitters forming the light source may be any suitabletype light emitting device, such as various forms of incandescent,fluorescent, halide, halogen, arc, or neon lamps. In many examples of afixture like 10, the emitters are solid state light emitters, just a fewexamples of which include electro luminescent (EL) devices, varioustypes of light emitting diodes (LEDs), organic light emitting diodes(OLEDs), planar light emitting diodes (PLEDs) and laser diodes. Forpurposes of further discussion, the light fixture 10 includes a lightsource formed by one or more lighting emitting diodes indicatedcollectively by the element labeled LED 11 in the diagram.

Although some light fixtures discussed in a system example later mayhave a single radio frequency (RF) type wireless transceiver, theexample light fixture 10 includes two RF wireless transceivers 13 and15. All fixtures will have at least one transceiver, but possibly notthe second transceiver; therefore the transceiver is indicated in dashedlines as a possibly optional component of the light fixture 10. Forexample, a fixture 10 configured as both a node and an edge gateway mayhave and utility both transceivers 13 and 15 (unless one transceiver,e.g. 5G cellular, can implement both types of communication). Fixturesoperating only as nodes may use only one transceiver. For the node-onlyfixtures, there may be no second transceiver, or there may be a built insecond transceiver that might be used in case of a need to reconfigure aparticular node to assume the function of an edge gateway (e.g. in theevent of a failure of another light fixture that previously operated asan edge gateway).

In the example, the first wireless transceiver 13 is of a first type,e.g. a Bluetooth Low Energy (BLE) transceiver, configured to communicateover a first radio frequency band. The first wireless transceiver 13 iscoupled to a non-coplanar antenna array 12. The first wirelesstransceiver 13 and non-coplanar antenna array 12 may be configured tooperate as a mobile asset detection device 14. The non-coplanar antennaarray 12 may, for example, include multiple discrete antenna elements inwhich at least one of the multiple antenna elements is in a differentplane than the other antenna elements of the array, in thisconfiguration, the non-coplanar antenna array 12 may also be referred toa multi-element antenna array 12. The number of discrete antennaelements forming the multiple discrete antenna elements may be three ormore discrete, non-coplanar antenna elements. In addition, the mobileasset detection device 14 may, as discussed in more detail withreference to another example, utilize a transceiver and a processor onboard the light fixture 10 as a detection transceiver and a detectionprocessor, respectively.

The second wireless transceiver 15 is of a second type, e.g. a WiFitransceiver, different from the first type (BLE) of transceiver; and thesecond wireless transceiver 15 is configured to communicate over asecond radio frequency band. The second radio frequency band (for WiFiin the example) at least partially overlaps the first frequency band(for BLE in the example). For example, BLE or other Bluetooth signalsuse frequencies between 2.4000 GHz and 2.4836 GHz (the “2.4 GHz band”),while WiFi signals are broadcast using frequencies in three 22-MHz-widesub-bands spaced out within the 2.4 GHz band. BLE and WiFi are used hereby way of non-limiting examples only. Other examples of suitabletransceivers include 3G, 4G or 5G cellular transceivers, Zigbeetransceivers, sub-gigahertz (e.g. 900 MHz) personal area network (PAN)transceivers, or the like.

The light fixture 10 also includes a driver 16 configured to supplypower to and control operation of the light source, in this example, theLEDs 11. As discussed more later, the example driver 16 draws power froman external source, such as alternating current (AC) mains 17 andprovides direct current (DC) to power the LEDs 11. Alternatively, the ACmains 17 may be replaced with or supplemented with a DC source, such asa solar power source, wind source or the like. The example driver 16 maybe an intelligent type device in that it is programmable and interfaceswith additional components in the light fixture 10. One aspect of such adriver is that the driver 16 provides a data bus 18 coupled to supportan exchange of data with and for other components of the fixture 10. Inthe light fixture 10, the data bus 18 supports exchange of data to andfrom the wireless transceivers 13 and 15. The data exchange over thedata bus 18 may be between the wireless transceivers 13 and 15 orbetween the driver 16 and either one of the wireless transceivers 13 and15.

Depending on the driver and bus design, the fixture components coupledon the data bus 18 use a suitable protocol to exchange data, commands,etc. For example, the driver 16 may poll the other components on thedata bus 18, and the other components will respond by sending any dataready for communication over the bus 18 back over the bus to the driver16. If intended for the driver 16, the driver 16 itself processes thedata (consumes the data). If the data received by the driver 16 over thedata bus 18 is intended for another component, the driver 16 sends thedata over the data bus 18 in a manner logically addressed to the otherfixture component.

Optionally, the light fixture 10 may include one or more sensors. By wayof example, the drawing shows a single sensor 19. Examples of sensorsrelating to lighting control include various types of occupancy andambient light sensors, a temperature sensor or light sensor coupled tothe LEDs 11 to provide feedback, or the like. The sensor 19, however,may be a sensor of a type not necessarily used to control the lightingprovided by the LEDs 11, such as an ambient temperature sensor, avibration sensor, an air pressure and/or humidity sensor, a microphoneor other audio input device, a still image or video image sensor, etc.The driver 16 may control the light fixture operation, particularly theLEDs 11, in response to data received from the sensor 19 over the databus 18; and/or the driver 16 may cause communication of sensor data toother equipment via the data bus 18 and either one or both of thewireless transceivers 13, 15. For example, occupancy sensing data from asensor 19 may be sent to other lighting devices within range using theBLE wireless transceiver 13.

The components shown in FIG. 3 may be integrated into a single housing(e.g., in a luminaire) or distributed spatially to any extent that iscompatible with successful bus signaling. For example, the light source11 and possibly the driver 16 may be in the luminaire component and someor all of the other electronics 13, 15, 19 may be located separately andconnected to the source 11 and possibly the driver 16 within theluminaire via the data bus 18.

In an operational example, a processor, such as a detection processor,may execute program instructions stored in the memory that configure thelight fixture 10 to perform functions. The functions may includedetecting a mobile asset within a service volume in response toreceiving a signal emitted by the mobile asset, for example, via anode/asset wireless link 189 of FIG. 1 or the like. The processor maydetermine a value related to the emitted signal as received via each ofthe multiple discrete antenna elements; and output data based on thedetermined value related to the emitted signal as received via each ofthe multiple discrete antenna elements. The light fixture 10 or 10 a maybe further configured to determine differences between the respectivedetermined values for inclusion in the outputted data.

To summarize the example, in a light fixture 10, the driver 16communicates with a BLE wireless transceiver 13, a WiFi wirelesstransceiver 15, and optionally a sensor 19 via a data bus 18. Power isderived by the driver from an AC source 17 and supplied to the wirelesstransceivers 13, 15 and the sensor 19, via a DC bias on the data bus 18or via a separate power and ground. The driver 16 also controls an LEDlight source 11. The data bus 18 conveys data to and from the wirelesstransceivers 13, 15, and from the sensor 19 to the driver 16. The databus 18 also conveys commands and data from the driver to the otherdevices 13, 15, 19.

A variety of smart drivers for light sources or other devices may beused to implement the driver 16. It may be helpful to consider asimple/high-level example with respect to the block diagram of FIG. 4.In the example of FIGS. 3 and 4, the LED light source 11 includes anumber of LEDs on a single drive channel. Although drivers withadditional channels (e.g. for independently controllable sets of LEDS)may be used, for this example, any single-channel LED driver 16 thatprovides sufficient controllable power to drive the selected LEDs 11 maybe used. The driver 16 includes one or more power supplies 20 thatobtain power from AC mains 17. One such power supply circuit 21 providesDC power to drive the LEDs 11 to emit light for illumination purposes.In the example, the power supply circuits 20 include an additional orauxiliary (Aux) power supply 22. The auxiliary power supply circuit 22provides power of an appropriate voltage and maximum current to providepower for other electronic components of the light fixture 10, such asthe wireless transceivers 13, 15 and the sensor 19 in the example ofFIG. 3. The auxiliary power may be provided over the data bus or over aseparate power bus (shown as a dotted line arrow).

Examples of suitable drivers 16 are available from eldoLED B.V. Thedriver 16 may receive power from AC mains, 100V AC to 488V AC, e.g. 120VAC or 220V AC. The driver 16, for example, may be a multi-volt inputdevice capable of driving the LEDs using power obtained from any ACsource 17 in a range of 120V AC to 227V. It is also possible toimplement the light fixture 10 with a low voltage DC power supply, suchas a 24V supply. As another alternative, the light fixture 10 may use abattery, wind or solar power source, as an alternative or a backup to ACmains power. The circuitry of the light fixture 10 may be locatedremotely from a luminaire that contains the actual LEDs 11, so that onlythe LEDs are included in the luminaire, and a remotely located driver 16would connect to the LEDs 11 to supply controlled current to drive theLEDs 11.

The driver 16 in the example also includes processor circuitry in theform of a central processing unit (CPU) 23 along with various memoriesone of which is shown at 24 for storing instructions for execution bythe CPU 23 as well as data having been processed by or to be processedby the CPU 23. The memory 24, for example, may include volatile andnon-volatile storage; and the program instructions stored in the memory24 may include a lighting application (which can be firmware), in thisexample, for implementing the processor functions of the light fixtureincluding light control functions as wells as communication relatedfunctions including some examples of the three dimensional locationdetermination.

The driver 16 also may include an input interface 25 for suitableconnection/communication of the driver 16 with other system elements,such as a light switch, dimmer or the like as a user input to controllighting operations. The driver 16 may also implement a clock (Clk) 27for timing related functions. The clock 27 may be a specific circuitwithin the driver 16 or implemented as a program controlled function ofthe CPU processor 23.

The driver 16 also includes a data bus interface 28 coupled to the CPU23. The data bus interface 28 is a circuit configured for connection tothe wires or for coupling to another type media forming the data bus 18and for providing appropriate signals over the media of the data bus 18carrying data for the driver and for other fixture components on thedata bus 18. In an eldoLED driver, the bus 18 is a two-wire bus andcarries data in a proprietary code protocol. The data bus interface 28in the driver 16 applies signals to such a bus in the protocol andsenses signals on the bus in that protocol that have been applied byother fixture components on the particular media implementation of thedata bus 18.

The two-wire bus and associated interface are described here by way ofnon-limiting examples only. It should be apparent that data busses usingmore than two wires, non-electrical (e.g., optical) busses, and wirelessbusses may be used in a light fixture 10; and for such alternate busimplementations, the driver 16 would have a corresponding alternateimplementation of the data bus interface 28.

The driver 16 may be implemented as a suitable chip set or may beimplemented as a single microchip device. In a single chip example, thepower supplies 20, the CPU 23, the memory 24, the input interface 26,any circuitry of the clock 27, and the data bus interface 28 are allincluded on a single chip and sometimes referred to as a “system on achip” or SoC implementation of a driver.

Although additional transceivers may be included, the example lightfixture 10 includes two transceivers of different types communicatingover radio frequency bands that may be the same but at least somewhatoverlap. Typical examples of radio-frequency wireless transceiverssuitable for lighting device or lighting system applications includeWiFi transceivers; BLE or other Bluetooth transceivers; third-generation(3G), fourth-generation (4G), fifth-generation (5G) or higher cellulartransceivers, Zigbee transceivers, sub-gigahertz (e.g. 900 MHz) personalarea network (PAN) transceivers, or the like. For purposes of discussionof a specific example, the fixture 10 of FIG. 3 includes a BLE typewireless transceiver 13 and a WiFi type wireless transceiver 15. Suchexample transceivers may be built in a variety of differentconfigurations. It may be helpful to consider simple/high-level examplesof two different types of transceivers with respect to the blockdiagrams of FIGS. 5 and 6. BLE and WiFi are used here by way ofnon-limiting examples only. FIG. 5 illustrates an example of the BLEtype wireless transceiver (XCVR) 13, and FIG. 6 illustrates an exampleof the WiFi type wireless transceiver (XCVR) 15.

The BLE wireless transceiver 13 of FIG. 5 includes power distributioncircuitry 31, which draws power from the driver 16 (FIGS. 3 and 4), viathe data bus 18 (or optionally via a separate power bus shown as adotted line arrow). The power distribution circuitry 31 converts thereceived power to one or more voltages and/or current levels suitable topower the various electronic circuits of the BLE wireless transceiver13. The WiFi wireless transceiver 15 of FIG. 6 includes powerdistribution circuitry 41 that similarly draws power from the driver 16and converts the received power to one or more voltages and/or currentlevels suitable to power the various electronic circuits of the WiFitransceiver 15. In the examples of FIGS. 3 to 5, the driver 16 providespower, which typically involves a wired connection. Where the data bus18 is wireless (e.g. RF or optical), there may be no such connection, inwhich case one or both transceivers may draw power from another source(not shown).

The BLE wireless transceiver 13 includes a data bus interface 32, andthe WiFi wireless transceiver 15 includes a data bus interface 42. Thedata bus interfaces 32, 42 of the transceivers are generally similar tothe data bus interface 28 of the driver 16 (FIG. 5), in that each of theinterfaces 32, 42 is a circuit configured for connection to the wires orcoupling to other type media, forming the data bus 18. The data businterface circuits 32, 42, like the data bus interface 28, also areconfigured for providing appropriate signals over the media of the databus 18 carrying data from the respective wireless transceiver 13 or 15and for sensing data signals on the data bus 18 to recover data for useby the respective wireless transceiver 13 or 15.

The BLE wireless transceiver 13 may also incorporate the mobile assetdetection device 14. The BLE receiver 36r may be configured to processRF beacon signals received via the multi-element antenna array 37. Themobile asset detection device 14 as discussed above may use processorson board the BLE wireless transceiver 13, such as CPU 34, to performfunctions of the detection processor. For example, CPU 34 in addition tobeing configured to function as a processor for performing BLE protocoland communication functions, may be further configured to performfunctions related to the detection of a mobile asset within a servicevolume.

Optionally, the BLE wireless transceiver 13 may include a high speeddata interface 33, and the WiFi wireless transceiver 15 may include ahigh speed data interface 43. If included, such additional interfaces33, 43 would be configured to provide high speed data exchange over asuitable higher speed data bus media (not shown), for example, betweenthe respective wireless transceivers 13, 15, e.g. for any applicationinvolving exchange of data in which the transceivers support two typesof radio communications at data rates higher than available over thedata bus 18 provided by the driver 16.

The illustrated example transceivers 13, 15 are smart devices in thatthey include processor and memory capabilities for programmedoperational control and data processing. Hence, the BLE transceiver 13includes a central processing unit (CPU) 34 and one or more memoriesshown collectively at 35 storing program instructions (which can befirmware) and configuration data, for implementing communications andany other operations, such as mobile asset detection, to be implementedby the logic of the transceiver 13. Similarly, the WiFi transceiver 15includes a central processing unit (CPU) 44 and one or more memoriesshown collective at 45 storing program instructions (which can befirmware) and configuration data, for implementing communications andany other operations to be implemented by the logic of the transceiver15. The circuitry of the CPUs may be thought of as individual processorsconfigured upon execution of program instructions from the respectivememories.

Each wireless transceiver 13 or 15 also includes physical (PHY) layercircuitry including components for transmitting and receiving RFwireless signals carrying data and associated circuitry interfacing tothe respective CPU for exchange of the data and for receivingoperational control instructions from the respective CPU. Although othercircuitry such as digital signal processors, analog-to-digital anddigital-to-analog converters, filters and amplifiers may be included;for simplified illustration purposes, the BLE PHY circuitry 36 and theWiFi PHY circuitry 46 are shown as including respective transmitters andreceivers. Hence, the BLE PHY circuitry 36 includes a BLE transmitter36t and a BLE receiver 36r; and the WiFi PHY circuitry 46 includes aWiFi transmitter 46t and a WiFi receiver 46r.

Each PHY circuitry connects to one or more antennas in or coupled to therespective transceiver. Hence, the BLE PHY circuitry 36 connects to amulti-element antenna array 37 that is specifically configured withmultiple discrete antenna elements at least one of which is non-coplanarwith the other discrete antenna elements of the antenna array 37. Theantenna array 37 is also configured for two way wireless communicationin the BLE frequency band. Similarly, WiFi PHY circuitry 46 connects toone or more antennas (collectively shown as one antenna 47) specificallyconfigured for two way wireless communication in the WiFi frequencyband.

Each of the transceivers 13, 15 shown by way of examples in FIGS. 5 and6, may be implemented as a system on a chip (SoC), although they couldbe implemented as more separate individual components, with eachillustrated component formed of one, two or more interconnected chips.Alternatively, the two transceivers might be implemented on a singlecombined system on a chip, for example, incorporating the different PHYcircuits for BLE and WiFi but including only one set of the othercomponents (e.g. the CPU, memory, bus interface).

Each transceiver 13 or 15, in the example, includes programming in amemory 35 or 45. At least a portion of the programming configures theCPU (processor) 34 or 44 to control communications over a respectivewireless communication frequency band using the applicable protocol.

In this way, the two PHY layer circuits 36, 46, as controlled by theassociated processors (CPUs) 34, 44, are configured to communicate overtwo frequency bands defined by the respective protocol standards, inthis case by the BLE standard and the WiFi standard respectively. Thebands, however, are not entirely separate and overlap at least to somedegree as specified in the two otherwise different standards.

The auxiliary channel functions as a general purpose data “bus,” meaningthat all attached devices share the channel physically at all times;thus, a signal placed on the data bus 18 by any device 16, 13, 15 or 19is detectable by any other device on the bus. The driver 16 alsoprovides power, for example, via the data bus 18. In an example, thedata bus 18 is a pair of conducting wires (FIG. 3), but buses havingmore than two wires, non-electrical (e.g., optical) buses, and wirelessbuses may also be used to implement data bus 18. All devices on the databus 18 are equipped to send and/or receive signals via the data bus in amanner intelligible to other devices on the data bus 18. All of thedevices on the data bus 18 have sufficient computational capability toexecute commands received via the data bus 18 and/or to encode data fortransmission via the data bus 18.

FIG. 7 illustrates a system 600 of wireless enabled light fixtures 10,10 a distributed about a space, for example, in or around a building ata premises. Each of the wireless enabled light fixtures 10 or 10 aincludes a light source such a LED source 11, a light source driver 16having a power supply to drive the light source 11 and a data businterface. Each wireless enabled light fixture 10 or 10 a furtherincludes a data bus 18 provided by the interface of the driver 16, and afirst wireless transceiver coupled to that data bus 18. Although othertypes of wireless transceivers could be used as the first type oftransceiver that is included in all of the fixtures 10, 10 a; in theexample system 600, the first transceiver is a BLE type transceiver 13configured to communicate over a first radio frequency band, e.g. overthe band specified in the BLE standard. When equipped with a BLE typetransceiver 13, the light fixture 10 or 10 a may be referred to as aradio frequency-enabled (RF-enabled) light fixture. Some or all of thelight fixtures 10, 10 a may include sensors 19.

In FIG. 7, the fixtures 10 a are indicated as type 1 light fixtures inthat they may only have one wireless transceiver, e.g. only the BLEtransceiver 13. Alternatively, they may include additional transceivers,but those transceivers may be inactive (e.g. awaiting activation toreconfigure a type 1 fixture 10 a as a type 2 fixture 10).

In the system example 600, each of two or more respective wirelessenabled light fixtures, referred to as type 2 light fixtures 10, furtherincludes a second wireless transceiver coupled to the data bus 18provided by the interface of the driver 16 of the respective lightfixture 10. The second wireless transceiver is of a second typedifferent from the first type. Although other types of wirelesstransceivers could be used as the second type of transceiver in lightfixtures 10; in the example system 600, the second wireless transceiveris a WiFi transceiver 15. Each second (e.g. WiFi) wireless transceiver15 is configured to communicate over a second radio frequency band (e.g.the band allocated for WiFi) that at least partially overlaps the firstfrequency band.

The elements 11 to 19 of the light fixtures 10, 10 a may be implementedby correspondingly numbered elements/circuits as described aboverelative to the example light fixture components in FIGS. 3 to 6.

The light fixtures 10, 10 a of the system 600 are arranged to providegeneral illumination about a premises of operations. In the system 600,however, the light fixtures 10 having two active wireless transceivers13, 15 may be configured for an additional communications relatedfunction. For example, each of the type 2 light fixtures 10 may haveprogramming in a memory accessible to one of the processors of thefixture 10 configuring the respective light fixture 10 as an edgegateway with respect to a number of others of the wireless enabled lightfixtures 10 a. At a high level, in the BLE/WiFi example, light fixtures10, 10 a in a zone or group (three of which are shown by way of anon-limiting example) may communicate with each other via BLE. Thelighting fixtures 10, 10 a in a group in turn may be arranged to providegeneral illumination in a respective zone or area of the premises. Thelighting fixtures 10 provide a gateway between the BLE based lightfixture communications of the respective groups and a WiFi network thatincludes all of the type 2 light fixtures 10 and a fog gateway 751.

The system 600 in the example of FIG. 7 therefore also includes the foggateway 751. An example of that gateway 751, discussed later withrespect to FIG. 8, includes a wireless transceiver of the second typewireless transceiver (e.g. another WiFi transceiver) configured forwireless network communications with the respective wireless enabledlight fixtures 10 using the second radio frequency band (e.g. the bandallocated for WiFi). The fog gateway 751 also includes a data networkinterface for communication via a data network 601 with other computers603, 605.

The data network 601 may be a local area network or a wide area networksuch as an intranet or the public Internet. The drawing shows a host orserver type network connected computer 603 and a laptop type userterminal device 605 as non-limiting examples of external equipment thatmay communicate with the system 600 via the network 601 and the foggateway 751, for various data gathering or control purposes.

As described in more detail later relative to FIG. 8, a processor in thefog gateway 751 may be coupled to the second type wireless transceiverof the fog gateway 751 and the data network interface. The fog gatewayprocessor is programmed or otherwise configured to cause the fog gateway751 to provide a gateway between wireless network communications via thesecond type (e.g. WiFi) transceivers of the respective wireless enabledlight fixtures 10 using the second (e.g. WiFi) radio frequency band andthe data network 601.

Edge gateway functionalities in light fixtures 10 may serve to translatemessages received via BLE 13 from other light fixtures intocommunications suitable for exchange with the fog gateway 751, forexample, via WiFi. The edge gateway functionalities in light fixtures 10may serve to translate messages received from the fog gateway 751 overWiFi for communication to other light fixtures 10 a over BLE.

The drawing shows an example of a mobile asset 621 at a location in thepremises served by the system 600. Although not shown in this example,the mobile asset 621 includes circuitry, such as a BLE transmitter, anRFID transmitter or the like, with a unique mobile asset identifier thatis detectable by the BLE transceiver and/or a sensor in the lightfixtures 10, 10 a.

The communications through the edge gateway functionalities of the lightfixtures 10 may relate to lighting operations. Lighting relatedcommunications, for example, may include lighting related sensor data orlight fixture status/health data to be sent upstream to the fog gateway751. Non-lighting sensor data may be similarly sent upstream to the foggateway 751. In the downstream direction from the fog gateway 751,lighting related communications, for example, may include lightingcommands (e.g. turn ON LEDs 11, turn OFF LEDs 11, dimming or the like);configuration setting data (e.g. to define members of a control group,to designate a light fixture to act as a zone controller or as an edgegateway in a group, or the like); or software or firmware updates forthe light fixtures 10, 10 a and possibly for a wall controller 625.

For more information about asset tracking via a system like system 600,attention may be directed to U.S. patent application Ser. No.15/916,861, filed Mar. 9, 2018, entitled, “Asset Tag Tracking System andNetwork Architecture,” the entire disclosure of which is incorporatedherein by reference. Although somewhat different types of transceiversare used for the wireless communications among light fixtures, moreinformation regarding a protocol and procedures for wirelesscommunications amongst light fixtures, wall switches, at least onegateway, etc. may be found in U.S. Pat. No. 9,883,570 issued Jan. 30,2018, entitled “Protocol for Lighting Control via a Wireless Network,”the entire disclosure of which is incorporated herein by reference.

The fog gateway 751 is configured for wireless data communication withthe type 2 light fixtures 10 configured as edge gateways. For example,the fog gateway 751 may be configured with a WiFi radio frequencytransceiver that is compatible with the WiFi radio frequency transceiver15 of each of the light fixtures 10. Although the gateway 751 may usespecial purpose hardware, the example utilizes an appropriatelyprogrammed computer platform.

In an operational example, the system 600 may perform various functionsto provide three dimensional location estimation services. For example,the mobile asset 621 may transmit a beacon signal containing the uniqueidentifier of the mobile asset. The beacon signal may be compatible withthe BLE transceiver 13 of the mobile asset detection device 14. Thelight fixture 10 a may receive the beacon signal via the multi-elementantenna array of the mobile asset detection device 14. The mobile assetdetection device 14 as discussed herein may be configured to process thereceived beacon signals to determine a value related to an attribute ofthe received signal for each of the respective discrete antenna elementsand extract the mobile asset's unique identifier from the receivedbeacon signal. The mobile asset detection device 14 may further processand generate information related to the signal attributes andinformation related to the mobile asset's 621 unique identifier. Forexample, a processor (shown in other examples) of the mobile assetdetection device 14 may be configured to generate information for athree dimensional location estimation based on the determined valuesrelated to the received signal attribute as received by the discreteantenna elements. The light fixture 10 a may forward the generatedinformation, depending upon a configuration of the system 600 to a lightfixture 10, which is functioning as an edge gateway, to the fog gateway751, or both the edge gateway and the fog gateway. For example, themobile asset detection device 14 may output a signal containing theinformation for three dimensional location estimation.

In an example, the fog gateway 751 may be configured to control thelight fixtures 10 and 10 a. The fog gateway 751 may further beconfigured to receive information related to the unique identifier ofthe mobile asset 621 and the information related to the determinedvalues of the signal attribute via the fog gateway radio frequencytransceiver (shown in the example of FIG. 8). The fog gateway 751 maydetermine differences between the determined signal attributes values ofthe radio frequency beacon signal received via the discrete antennaelements. The fog gateway 751 may send, via the data communicationnetwork 601, information related to the determined differences the radiofrequency beacon signal received via the discrete antenna elements ofthe mobile asset and information related to the unique identifier to aserver, such as 603. The fog gateway 751 may also be configured toreceive signals containing the information for three dimensionallocation estimation from the radio frequency-enabled nodes. Theinformation for three dimensional location estimation may, for example,include the differences between the respective determined values relatedto the received signal between each of the discrete antenna elements ofthe multi-element antenna array. The server 603 may be configured toreceive information related to the determined differences of the radiofrequency beacon signal and the information related to the uniqueidentifier of the mobile asset sent via the fog gateway 751. The server603 may be by programmed or otherwise configured to perform the threedimensional location estimation in response to the data based on thedetermined values of the signal attribute. The three-dimensionallocation estimate may be provided in Cartesian or polar coordinates withrespect to the service zone, GPS coordinates with altitude indication,or some other form of three dimensional coordinate system. The server603 may deliver the three dimensional location estimate to the foggateway 751 or to the computer or laptop type user terminal 605. The foggateway 751 or the laptop type user terminal 605 may be furtherconfigured to analyze the three dimensional location estimate withrespect to maps, coordinates or some other data structure to determinewhether the mobile asset 621 is authorized to be at the estimatedlocation. In addition or alternatively, the determination may also bewhether the estimated location of the mobile asset 621 is within apredetermined distance and/or altitude of an exclusion zone, e.g. 100meters, an altitude of 2000 feet or the like.

FIG. 8 is a functional block diagram of a general-purpose computersystem 751, by way of just one example of a hardware platform that mayperform the functions of the fog gateway. The example 751 will generallybe described as an implementation of a server or host type computer,e.g. as might be configured as a blade device in a server farm or in anetwork room of a particular premises. Alternatively, the computersystem 751 may comprise a mainframe or other type of host computersystem capable of performing location determination services or the likevia the network 601 and the on-premises WiFi network formed with type 2light fixtures 10.

The computer system 751 in the example includes a central processingunit (CPU) 752 formed of one or more processors, a main memory 753, massstorage 755 and an interconnect bus 754. The circuitry forming the CPU752 may contain a single microprocessor, or may contain a number ofmicroprocessors for configuring the computer system 751 as amulti-processor system, or may use a higher speed processingarchitecture. The main memory 753 in the example includes ROM, RAM andcache memory; although other memory devices may be added or substituted.Although semiconductor memory may be used in the mass storage devices755, magnetic type devices (tape or disk) and optical disk devices maybe used to provide higher volume storage. In operation, the main memory753 stores at least portions of instructions and data for execution bythe CPU 752, although instructions and data are moved between memory 753and storage 755 and the CPU 752 via the interconnect bus 754.

The computer system of the fog gateway 751 also includes one or moreinput/output interfaces for communications, shown by way of example asinterface 759 for data communications via the network 601 as well as aWiFi type wireless transceiver 758. Each interface 759 may be ahigh-speed modem, an Ethernet (optical, cable or wireless) card or anyother appropriate data communications device. The physical communicationlink(s) to/from the interface 759 may be optical, wired, or wireless(e.g., via satellite or cellular network). Although other transceiverarrangements may be used, the example fog gateway 751 utilizes a WiFitype wireless transceiver 758 similar to the WiFi type wirelesstransceivers 15 in the light fixture and component examples of FIGS. 3and 6 described above. The WiFi type wireless transceiver 758 enablesthe fog gateway 75 to communicate over-the-air with the WiFi typewireless transceivers 15 in the edge gateways implemented in lightfixtures 10 in the system 600 of FIG. 7.

Although not shown, the computer platform configured as the fog gateway751 may further include appropriate input/output ports forinterconnection with a local display and a keyboard and mouse or with atouchscreen or the like, serving as a local user interface forconfiguration, programming or trouble-shooting purposes. Alternatively,the operations personnel may interact with the computer system of thefog gateway 751 for control and programming of the system from remoteterminal devices via the Internet or some other link via any network601.

The computer system implementing the fog gateway 751 runs a variety ofapplications programs and stores various information in a database orthe like for control of the fixtures, wall controllers and any otherelements of the lighting system 600 and possibly elements of an overallbuilding managements system (BMS) at the premises. One or more suchapplications, for example, might enable asset tracking, lighting controlthrough the fog gateway and/or lighting control based on input from thesensors 19 or the wall controller 625.

The example FIGS. 7 and 8 show a single instance of a fog gateway 751.Of course, the fog gateway functions may be implemented in a distributedfashion on a number of similar platforms, to distribute the processingload. The hardware elements, operating systems and programming languagesof computer systems like that of the fog gateway 751 generally areconventional in nature, and it is presumed that those skilled in the artare sufficiently familiar therewith to understand implementation of thepresent system and associated lighting control technique using suitableconfiguration and/or programming of such computer system(s).

Examples of the mobile asset detection device or system include anantenna array having multiple discrete antenna elements disposed in anon-coplanar arrangement on or within an RF node as well as capabilitiesfor measuring properties (e.g., differential time of arrival) of RFsignals sensed by a processor coupled to the multi-element antennaarray. Differences in time of arrival of a signal at the multi-elementantenna may be used to estimate the direction from which the signal hascome (i.e., the bearing of the signal's source). Thus, in an example, astreetlight luminaire equipped with the mobile asset detection deviceaccording to an example may be configured to estimate the bearing and/orrange of a mobile asset, such as an airborne drone, transmittingappropriate RF beacon signals in the vicinity of the streetlightluminaire. The principles of such estimation are described below.

FIG. 9 illustrates an example of an estimation of the bearing of asignal source using two antenna in a plane. In order to understand thebenefit of estimating a location in three dimensions, it may be helpfulto understand the concepts for making a two-dimensional locationestimate. First principles of a location estimation in two dimensionsare shown in FIG. 9. Depicted in FIG. 9 is the transmission of a radiosignal from an RF source, such as RF node 110 a of FIG. 1, at point A toan antenna array (shown as rounded squares) with discrete antennaelements 91 and 92 at points B and C, respectively. The radio signal maybe a beacon signal from a mobile asset. Each antenna element 91 and 92receives the beacon signal.

In the example of FIG. 9, the direction or bearing of the RF source atpoint A is defined as the angle 0 between the line segment BC connectingthe two antenna elements 91 and 92, and the line AM connecting point Awith the midpoint M of the line segment BC connecting the antennaelements 91 and 92. The RF signal(s) from the RF source at point A reachantenna element 91 at point B by path AB and reach antenna element 92 atpoint C by path AC. If line BE is drawn to make an isosceles triangleABE, then path AB is shorter than path AC by a distance A. Thus, thesignal from the RF source at point A may reach antenna element 91 atpoint B more quickly than it reaches antenna element 92 at point C, thetime-of-arrival difference being Δ/cm seconds (where cm is the speed oflight in the ambient medium, e.g., air). This time-of-arrival differenceis also termed a “phase difference,” and may be measured by comparingthe output signals of antenna element 91 at point B and antenna element92 at point C.

Since the length and orientation of line segment BC are known, thebearing θ may be calculated from the phase difference A/cm. (In thisdiscussion, all antenna are for simplicity presumed to be point-size,and the distance from the source to the antenna is presumed to be muchlarger than the distance between the antenna elements 91 and 92. Giventhese assumptions, Δ/cm is effectively independent of range and uniquelydetermines the bearing θ. These assumptions will hold usually andapproximately for all the disclosed examples.

However, in FIG. 9, it is clear by symmetry that a signal from an RFsource at point A′ having a bearing −θ would also arrive at the antennaelement 91 at point B and antenna element 92 at point C with a phasedifference A/cm. Therefore, two antenna elements, such as 91 and 92, donot suffice to uniquely estimate a location of an RF source in twodimensions. In order to uniquely estimate a location of an RF source, anadditional antenna element would be advantageous.

FIG. 10 shows an example of a disambiguation of a bearing using threeantenna elements in a plane. Three or more antenna elements may be usedto unambiguously determine the bearing of a source in two dimensions.The antenna element arrangement shown in FIG. 10 includes a thirdantenna element 93 at point F in addition to antennas elements 91 and92. By inspection, path AF is longer than path A′F; a signal transmittedfrom an RF source at point A therefore gives different phase readings atF than the same transmitted signal from an RF source at point A′. Fromthe phase differences between antenna elements 91 at point B, 92 atpoint C, and 93 at point F, the bearing of an RF source therefore can becalculated unambiguously. In the case depicted, the RF source is atpoint A and its bearing is θ, not −θ as if the signal source was as atpoint A′. The location of the RF source at point A may be estimatedaccurately by using three antenna elements 91 at point B, 92 at point C,and 93 at point F, as well as other signal attributes to determine rangefrom the respective antenna elements 91-93.

In general, the bearing of an RF source (e.g., a mobile asset) may beunambiguously estimated in two dimensions from phase differences amongthree or more non-coplanar antenna elements. The exact positions of thethree antenna elements 91, 92 and 93 are superfluous as long as thethree antenna elements 91, 92 and 93 are not all in a straight line.

The above concepts may be extended to perform a three-dimensionallocation estimate of an RF source.

FIG. 11 illustrates an example of a relationship of a signal source in3-dimensional space to an antenna array for use in providing athree-dimensional location estimation of a signal source, such as amobile asset described in the examples of FIGS. 1, 2 and 7. Similarconcepts as applied in the example of FIG. 10 are also applicable in athree dimensional location estimation of an RF source. The threedimensional location may be calculated from phase differences among 4 ormore non-coplanar antenna elements. The exact positions of the 4 or morenon-coplanar antenna elements are superfluous as long as at least oneantenna of the 4 or more non-coplanar antenna elements is not in acommon plane with the others.

In the example of FIG. 11, an RF node 1110 is shown with a multi-elementantenna array 1120 that includes four non-coplanar antenna elements P,Q, R and S. Non-coplanar meaning that at least one of the four antennaelements P, Q, R or S is not in the same plane as the other threeantenna elements. Other components of RF node 1110, such as BLEtransceiver 13 or light source 11, are not shown for ease ofillustration, but the RF node 1110 may be configured in a manner similarto an RF node or lighting device such as 10 in FIG. 3. The fournon-coplanar antenna elements P, Q, R and S (indicated by dots) may bepoints that define the vertices of a tetrahedron. Phase differencesmeasured by a tetrahedral antenna array, such as 1120, enablescalculation of the bearing of a signal source, such as Tin 3-dimensionalspace. The relationship of the signal source T in three-dimensionalspace to a tetrahedral multi-element antenna array 1120 and geometry ofthe multi-element antenna array 1120 are by way of example but may bedifferent depending upon the use. In an example, a luminaire may likelyinclude a lighting fixture that operates as an RF node. In anotherexample arrangement of the antenna elements, the multi-element antennaarray of the RF node may have a horizontally oriented antenna pair and avertically oriented antenna pair that is non-coplanar with thehorizontal pair.

As shown in FIG. 11, the RF node 1110 may be a pole-mounted RF nodehaving a multi-element antenna array 1120 coupled at or near the top ofthe pole 1150. Since the four antenna (P, Q R and S) are, in general, atdifferent distances from any external RF source T (e.g., a drone), thesource T cannot be at the same distance from all 4 antenna elementssimultaneously. A signal emitted by source T (may travel as shown by thetransmission paths indicated by the dot-dash lines) therefore arrives atthe four antenna elements with up to 4 phase delays that uniquelycorrespond to the source T's location.

When the source T is relatively distant from the multi-element antennaarray 1120, range information may be difficult to extract using such anarrangement. However, when the source T is relatively close to themulti-element antenna array 1120, both bearing and range information maybe extractable as explained in more detail below.

The illustrated examples provide a structure for obtaining the bearingof a mobile asset. The term “bearing” as used herein refers to adirection of an object, such as an RF signal source in the examples ofFIGS. 9 and 10, from a reference direction or point. In the examples ofFIGS. 9 and 10, the bearing corresponds to the direction of an RF sourcefrom the location of an RF node.

However, the bearing does not provide the distance from the respectiveantenna element to an RF source (i.e. range), measurements and/orcalculations in addition to those described are used to provide a rangeestimation with respect to the RF source.

For example, if the RF source transmission power is known (e.g., becausethe type of transmitter used by a given mobile asset class is known froma database, or because transmit-strength information is encoded in thetransmitted signal), then the range to the RF source from the RF nodemay be estimated by comparing received signal strength (RSS) to transmitsignal strength. Note that this assumes omnidirectional transmission,for which RSS drops by the inverse square of the range regardless ofdirection; such transmission is typical for mobile assets. Range canalso be estimated by timed-response techniques: e.g., the luminairesystem transmits a command to the asset, such as a “Transmit a pulsecontaining your identification” command, and measures the time fromcommand transmission until a response is received. In another example,mobile assets may be configured to regularly broadcastself-identification information, such as a mobile asset identifier (ID),in a digitally coded manner. The mobile asset ID information may bereceived by an RF node and be used for asset-specific communication(e.g., commands from a node that elicit pulse transmissions from amobile asset or otherwise affect its behavior), as well as otherpurposes. For example, range may be determined using information such asgiven prior knowledge of a command response delay, a round-trip pingtime, or the like. Range may also be estimated using radar methods. Forexample, the RF-node within a light fixture emits an RF signal andmeasures the time until a reflection is received from the mobile asset.

In addition, the reflective radar methods in the above examples may becombined with angle-of-arrival and other techniques to estimate assetposition. Use of multiple bearing and range estimation techniques may(1) improve position estimate accuracy and (2) in some casesdisambiguate location estimates in cluttered (e.g., urban or enclosed)environments where signal reflections can confound straightforwardestimation.

For example, the multiple RF antenna elements (P, Q, R and S) may bedisposed on or within an RF node, such as 1110 as well as capabilitiesfor measuring properties (e.g., differential time of arrival) of RFsignals detected at the multiple RF antenna elements of the antennaarray. Differences in time of arrival of a signal at the multipleantenna elements may be used to estimate the direction from which thesignal has come (i.e., the bearing of the signal's source). Thus, in anexample, a streetlight luminaire may be equipped with a multi-elementantenna array, such as 1120 according to an example can estimate thebearing and/or range of an airborne drone transmitting appropriate RFsignals in its vicinity.

While the above examples noted that four non-coplanar antenna elementsin a multi-element antenna array provide unambiguous bearing estimatesin 3-D space, some directional information may be derived from phasedata gathered by only two (2) or three (3) antenna elements, and evenambiguous estimates of direction and/or range, if collated among two (2)or more nearby nodes, can in some cases be combined to yield unambiguousor less-ambiguous location estimates. Therefore, in some examples, theinformation provided to the edge gateways may be information combinedfrom multiple RF nodes that deliver information to the same or differentedge gateways.

Such combining of information from multiple RF nodes may improve themobile asset location estimate accuracy, and, in some cases may be usedresolve ambiguities, such as, for example, those created by signalreflections in cluttered environments.

A specific example of combining information may include determining aDoppler shift, i.e., spectral shifting of a signal due to relativemovement, may also be exploited in some example. In the example,determined Doppler shift information may be used to estimate transmittermotion and location: e.g., the Doppler effects measured by two or morenon-collocated stationary antenna will in general depend upon and changewith the location of the moving transmitter and differ from antenna toantenna. It should be noted that the Doppler shift of a signal from amoving source, as measured by a stationary receiver, depends on sourcelocation, source velocity vector, and receiver location. Dopplerinformation may be combined with phase differences and other RF signalmeasurements and be used by a computational device as described in theabove examples to produce, hone, or disambiguate estimates oftransmitter location.

In addition to enabling use of the multi-element antenna array, thedescribed examples also allow the receipt and employment by one or morenodes in the network of various kinds of data collected by mobile assets(such as movement, temperature, light detection patterns, compassheadings, route histories, video, and any other data types from whichlocational information may be derived or the like) and the combining ofthe various kinds of collected data with luminaire-based or lightfixture data based may be used to further improve asset locationestimates.

In some examples, it is noted that received signal strength may not be agood indicator because of depleted battery. So a close asset with adepleted battery may have a weak signal strength in which case usingsignal strength as a proxy for distance provides erroneous indicationsof distance. Assets may include approximate transmit power to allow moreaccurate position determination.

It may be helpful to explain an example of a process for estimating alocation of a mobile asset within a service volume with reference to asystem. FIG. 12 is a flowchart depicting an example of a process flowfor performing a three-dimensional location estimation as described withreference to the foregoing examples, such as the systems described withreference to FIGS. 1, 2 and 7. The process 1200 may be performed by aprocessor located in or at a lighting device equipped with a mobileasset detection device, such as CPU 34 of FIG. 5 or the like. Asdescribed with reference to other examples, a mobile asset detectiondevice may be coupled to a respective light fixture of multiple lightfixtures distributed in a service zone, and may also include an antennaarray having multiple discrete antenna elements. At step 1210, themobile asset detection device such as 14 of FIG. 3 may receive a radiofrequency beacon signal emitted from a mobile asset, such as 125 of FIG.1 or 621 of FIG. 7, by a mobile asset detection device.

Based on outputs of the mobile asset detection system generated inresponse to the received radio frequency beacon signal, a value of asignal attribute of the radio frequency beacon signal as received viaeach discrete antenna element of the antenna array coupled to therespective light fixture may be determined by the processor of themobile asset detection device (1220). A signal attribute value may bedetermined for each discrete antenna element. So in the example of FIG.11, a signal attribute value may be determined for each of antennaelements P, Q, R and S. For example, one or more of the determinedsignal attribute values may be determined based on information containedin the received beacon signal. The determined signal attribute valuefrom each respective discrete antenna element may be stored in a memory,such as 35 of the BLE XCVR 13. The determined signal attribute value maybe indicative of a quantitative value of a signal phase, an angle ofarrival, a received signal strength, or a time delay of arrival.

The processor may generate information for a three dimensional locationestimation based on the determined values related to the received signalattribute as received by the discrete antenna elements. For example,processor, at 1230, may determine differences between the determinedvalues of the signal attributes of the radio frequency beacon signalreceived via the discrete antenna elements. Returning to the example ofFIG. 11, the discrete antenna elements P. Q. R and S may all have adifferent signal attribute value depending upon the location of signalsource T. For example, the determined differences between the determinedvalues of the signal attribute may be the determined differences of oneor more of the signal attributes, such as signal phase, angle ofarrival, received signal strength, or time delay of arrival, betweeneach of the discrete antenna elements.

The determined differences may be processed at 1240 to estimate athree-dimensional location of the mobile asset with respect to themobile asset detection system for a time when the mobile assettransmitted the radio frequency beacon signal. For example, whenestimating the three-dimensional location, the processor may access adatabase containing data identifying a known physical location of themobile asset detection system. The data identifying physical location ofthe mobile asset detection system may be used in the processing toestimate the three-dimensional location of the mobile asset in theservice volume.

Based on the estimated location, the processor may output an alertsignal. A determination to output the alert may be based further ondetermining whether or not the mobile asset is authorized to be at orwithin a predetermined proximity (e.g., 150 meters or the like) theestimated location. For example, a processor may access a look up tablewith coordinates of exclusion zones or security perimeters thatcorrespond to the coordinate system of the location estimate.Alternatively, the processor may be configured to translate locationestimate coordinates to other coordinate systems, or vice versa.

In another example, the beacon signal may include a light fixtureidentifier associated with the RF node transmitting the beacon signal.The processor may be configured to associate a light fixture identifierwith the values of the determined signal attribute of the radiofrequency beacon signal received via the discrete antenna elements. Theprocessor may further be configured to use the light fixture identifierto obtain data identifying a known physical location of the respectivelight fixture within the service volume; and use the data identifyingthe physical location of the mobile asset detection system in theprocessing to estimate the three-dimensional location of the mobileasset in the service volume.

The asset tracking tags 1320 may be small, smart, powered devices thatexchange radio signals with nodes having networked radio capability,such as the network of RF-enabled wireless communication nodes, such as110 or 110 a of FIG. 1. The tag 1321 is active in that it activelycommunicates to obtain and it actively processes data and sendsinformation. A tag operates in a wireless network of the RF-enabledlighting devices (described in detail with respect to FIG. 2). Asdescribed above, the described system examples are configured to enablethe asset tracking tags 1320 to send messages designated for delivery,for example, to one of a number of edge gateways, or to the fog gateway(as described earlier). It may be appropriate to discuss an exampleconfiguration of one of the asset tracking tags 1320 in more detail withreference to asset tag 1321.

In order to communicate, the asset tracking tags 1321 may include anantenna 1325, a radio frequency (RF) transmitter or transceiver 1345, aprocessor 1365, a memory 1355, and a sensor 1385. The antenna 1325 maybe coupled to the RF transmitter or transceiver 145, and configured toreceive and/or emit signals within a specific radio frequency band thatis compatible with the RF transmitter or receiver 1345. The RFtransmitter/transceiver 1345 may be a Bluetooth transmitter/transceiver,a Zigbee transmitter/transceiver, a radio frequency identifier (RFID)transmitter/transceiver, a Wi-Fi transmitter/transceiver or otherwireless communication transmitter/transceiver suitable for use in anasset tracking tag.

The processor 1365 may be coupled to the RF transmitter/transceiver1345, the power supply 1375, the memory 1355 and the sensors 1385. Theprocessor 1365 may send signals to the RF transmitter/transceiver 1345for transmission and/or receive signals received by the RFtransmitter/transceiver 1345 obtained via the antenna 1325.

The memory 1355 may be a non-volatile memory, random access memory(RAM), read only memory (ROM), a Flash memory or the like. The memory1355 may be configured to store programming instructions executable bythe processor 1365. Upon execution of the programming instructionsstored in the memory 1355, the processor 1365 may be configured toperform different functions. Examples of the different functions thatthe processor 1365 may be configured to perform upon execution of theprogramming code or instructions are described in more detail withreference the previous examples of FIGS. 1-7 and 12. The differentfunctions may be internal to the processor 1365. For example, theprocessor 1365 may include a counter that is monitored by the processor1365. At a predetermined count, the processor 1365 may transmit asignal, such as a beacon signal.

The power supply 1375 may be a battery, a solar cell, or other form ofquickly available power that is suitable for driving the variouselectronics associated with the asset tracking tag 1321 components, suchas the RF transmitter/transceiver 1345, the processor 1365, the memory1355 and/or the sensor 1385.

The sensor 1385 may be configured to detect and respond to an event thatoccurs in the environment in which the asset tracking tag 1321 islocated. For example, the sensor 1385 may be, for example, one or moreof an accelerometer, thermometer, a photocell, a microphone, a shocksensor, or the like. In response to a detected stimulus (e.g.,temperature, movement, noise, ambient light), the sensor 1385 may outputa signal causing the processor 1365 to perform a function or process.

As described above, each of the asset tracking tags, such as 1321, maybe configured to transmit signals, such as a beacon signal and/or othersignals, to one or more of RF-enabled wireless communication nodes. Theasset tracking tags 1320 may also be configured to receive signals, forexample, from the fog gateway via an edge gateway and the wirelessRF-enabled nodes.

The location estimation processes described herein may be implemented byexecution of programming code by a processor such as one or more ofthose described above.

Program or data aspects of the technology discussed above therefore maybe thought of as “products” or “articles of manufacture” typically inthe form of executable programming code (firmware or software) or datathat is carried on or embodied in a type of machine readable medium.

“Storage” type media include any or all of the tangible memory oflighting fixtures 10 or drivers 16 or transceivers 13, 15 thereof, aswell as various computer platforms, such as that of the fog gateway 751,a host or server computer 603 or user terminal 605 on an externalnetwork 601, or any of the various processors or the like, such asvarious volatile or non-volatile semiconductor memories, tape drives,disk drives and the like, which non-transitory devices may providestorage at any time for executable software or firmware programmingand/or any relevant data or information. All or portions of theprogramming and/or configuration data may at times be communicatedthrough the Internet or various other telecommunication networks. Suchcommunications, for example, may enable loading of the data orprogramming from one computer or processor into another, for example,from the fog gateway 751, a management server or host computer of alighting system or BCAS management system type service provider into anyof the light fixtures 10. Thus, another type of media that may bear theprogramming or data elements includes optical, electrical andelectromagnetic waves, such as used across physical interfaces betweenlocal devices, through wired and optical landline networks and overvarious air-links. The physical elements that carry such waves, such aswired or wireless links, optical links or the like, also may beconsidered as media bearing the software. As used herein, unlessrestricted to non-transitory, tangible or “storage” media, terms such ascomputer or machine “readable medium” refer to any medium thatparticipates in providing instructions to a processor for execution.

The programming or data for estimating the three-dimensional location ofa mobile asset may be embodied in at least one machine readable medium,one or more of which may be non-transitory. For example, if downloadedto a light fixture 10, the programming or data could be stored in ahardware device that serves as the memory/storage of the driver ortransceiver(s) of the light fixture. The memory/storage is an example ofa non-transitory type of media. By way of another example, at times,executable operational programming, including programming and/or datafor the three-dimensional location estimation, may reside in thememory/storage of the fog gateway, a server or user terminal device andbe streamed over the network media to one or more light fixtures. Inthese later examples, the signal(s) on the network would be transitoryin nature. However, the buffer memory and any memory or registersinternal to the processor memory, or any hardware storage device used bythe fog gateway, server or other computer to maintain the programmingand any data or to prepare selected programming or data for transmissionover the network would be additional examples of non-transitory media.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”“includes,” “including,” or any other variation thereof, are intended tocover a non-exclusive inclusion, such that a process, method, article,or apparatus that comprises or includes a list of elements or steps doesnot include only those elements or steps but may include other elementsor steps not expressly listed or inherent to such process, method,article, or apparatus. An element preceded by “a” or “an” does not,without further constraints, preclude the existence of additionalidentical elements in the process, method, article, or apparatus thatcomprises the element.

In addition, in the foregoing Detailed Description, it can be seen thatvarious features are grouped together in various examples for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the claimed examplesrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, the subject matter to be protected liesin less than all features of any single disclosed example. Thus thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separately claimed subjectmatter.

Unless otherwise stated, any and all measurements, values, ratings,positions, magnitudes, sizes, and other specifications that are setforth in this specification, including in the claims that follow, areapproximate, not exact. They are intended to have a reasonable rangethat is consistent with the functions to which they relate and with whatis customary in the art to which they pertain.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

What is claimed is:
 1. A method, comprising: receiving a radio frequencybeacon signal emitted from a mobile asset by a mobile asset detectiondevice, wherein the mobile asset detection device: is coupled to arespective light fixture of multiple light fixtures distributed in aservice volume, and includes an antenna array having multiple discreteantenna elements; based on outputs of the mobile asset detection systemgenerated in response to the received radio frequency beacon signal,determining a value of a signal attribute of the radio frequency beaconsignal as received via each discrete antenna element of the antennaarray coupled to the respective light fixture, wherein a signalattribute value is determined for each of the discrete antenna element;determining, by a processor, differences between the determined valuesof the signal attribute of the radio frequency beacon signal receivedvia the discrete antenna elements; and processing the determineddifferences, to estimate a three-dimensional location of the mobileasset with respect to the mobile asset detection system for a time whenthe mobile asset transmitted the radio frequency beacon signal.
 2. Themethod of claim 1, further comprises: accessing, by the processor, adatabase containing data identifying a known physical location of themobile asset detection system; and using the data identifying physicallocation of the mobile asset detection system in the processing toestimate the three-dimensional location of the mobile asset in theservice volume.
 3. The method of claim 1, further comprising:associating a light fixture identifier with the values of the determinedsignal attribute of the radio frequency beacon signal received via thediscrete antenna elements; using, by the processor, the light fixtureidentifier to obtain data identifying a known physical location of thelight fixture within the service volume; and using the data identifyingthe physical location of the light fixture within the service volume inthe processing to estimate the three-dimensional location of the mobileasset in the area.
 4. The method of claim 1, wherein the determineddifferences between the values of the determined signal attribute aredetermined differences of one or more of signal phase, angle of arrival,received signal strength, or time delay of arrival between each of thediscrete antenna elements.
 5. The method of claim 1, further comprising:outputting, by the processor, based on the estimated three-dimensionallocation of the mobile asset, an alert signal based on determiningwhether or not the mobile asset is authorized to be at or within apredetermined proximity to the estimated location.
 6. A system,comprising: a plurality of radio frequency-enabled mobile assetdetection devices configured to detect signals transmitted by a radiofrequency-enabled mobile asset within a service volume, the plurality ofradio frequency-enabled mobile asset detection devices being distributedwithin the service volume, each radio frequency-enabled mobile assetdetection device including: an antenna array having multiple discreteantenna elements, a detection processor, and a detection transceiver, afog gateway, the fog gateway comprising: a fog gateway radio frequencytransceiver communicatively coupled to the plurality of mobile assetdetection devices, wherein the detection processor in each radiofrequency-enabled mobile asset detection device is configured to:receive via each discrete antenna element of the antenna array a beaconsignal transmitted by the mobile asset, the beacon signal including aunique identifier of the mobile asset; determine a value of a signalattribute of the beacon signal received via each discrete antennaelement of the antenna array; and forward information related to theunique identifier of the mobile asset and information related to thedetermined values of the signal attribute, to the fog gateway radiofrequency transceiver; and at least one processor coupled to communicatethrough the fog gateway radio frequency transceiver and configured to:obtain a three-dimensional estimate, based on the forwarded information,of a location within the service volume of the mobile asset indicated bythe information related to the unique identifier of the mobile asset. 7.The system of claim 6, further comprising: an edge gateway comprising: afirst edge transceiver, a second edge transceiver, wherein the secondedge transceiver is configured to communicate over a radio-frequencyband at least some different from a radio-frequency band utilized by thefirst edge transceiver; and an edge processor; wherein the edge gatewayprocessor is coupled to the detection processor via a wireless linkbetween the second edge transceiver and a respective detectiontransceiver of each of a plurality of the radio frequency-enabled mobileasset detection devices.
 8. The system of claim 6, wherein: thedetection processor is further configured to determine differencesbetween the values of the determined signal attribute of the radiofrequency beacon signal received via the discrete antenna elements; andthe forwarded information related to the determined values of the signalattribute includes the determine differences.
 9. The system of claim 6,wherein when obtaining the estimated location within the service volumeof the mobile asset, the at least one processor is further configuredto: receive the forwarded information; identify: a first signalattribute difference between the determined signal attribute of a firstdiscrete antenna element and the determined signal attribute of a seconddiscrete antenna element, a second signal attribute difference betweenthe determined signal attribute of the first discrete antenna elementand the determined signal attribute of a third discrete antenna element,and a third signal attribute difference between the determined signalattribute of the second discrete antenna element and the determinedsignal attribute of the third discrete antenna element; and obtain thethree-dimensional estimate of the location of the mobile assetassociated with the mobile asset identifier, based on the first, secondand third signal attribute difference.
 10. The system of claim 6,further comprising: a fog gateway processor coupled to the fog gatewayradio frequency transceiver and communicatively coupled to a datacommunication network; and a server communicatively coupled to the datacommunication network, wherein the fog gateway processor is configuredto: receive the information related to the unique identifier of themobile asset and the information related to the determined values of thesignal attribute via the fog gateway radio frequency transceiver; andsend, via the data communication network, the information related to theunique identifier of the mobile asset and data based on the determinedvalues of the signal attribute to the server, and wherein the server isconfigured to: receive the information related to the informationrelated to the unique identifier of the mobile asset and the data basedon the determined values of the signal attribute and perform thelocation estimation in response to the data based on the determinedvalues of the signal attribute.
 11. The system of claim 10, wherein thefog gateway is further configured to: receive the estimated locationfrom the server, wherein the estimated location is a three-dimensionallocation within the service volume from which the beacon signal wastransmitted by the mobile asset; and based on the estimated location,generate a status message indicating a status of the mobile asset withrespect to the estimated location.
 12. The system of claim 10, whereinthe fog gateway is further configured to: access a database containinglocations of signal obstructing structures, security perimeters, andexclusion zones within a service volume, wherein the exclusion zones arethree dimensional volumes within the service volume in which the mobileasset requires authorization to enter or is prohibited from entering.13. The system of claim 6, further comprising: a plurality of radiofrequency-enabled light fixtures distributed over a service volume, eachof the plurality of radio frequency-enabled light fixturescommunicatively coupled to the fog gateway, and each light fixturecomprising: a light source for illuminating a portion of the servicevolume, wherein each of the mobile asset detection devices is collocatedwith a respective one of the plurality of radio frequency-enabled lightfixtures distributed over the service volume.
 14. The system of claim 6,wherein a mobile asset is an automobile, a ground-based robotic device,a bus, an unmanned aerial vehicle, or a radio frequency-enabled assettracking tag coupled to a movable device.
 15. The system of claim 6,further comprising: a fog gateway processor coupled to the fog gatewayradio frequency transceiver and communicatively coupled to datacommunication network; and a server communicatively coupled to the datacommunication network, wherein the fog gateway processor is configuredto: receive the information related to the unique identifier of themobile asset and the information related to the determined values of thesignal attribute via the fog gateway radio frequency transceiver; anddetermine differences between the determined signal attributes values ofthe radio frequency beacon signal received via the discrete antennaelements; send, via the data communication network, the informationrelated to the determined differences of the radio frequency beaconsignal received via the discrete antenna elements of the mobile assetand the information related to the unique identifier to the server, andwherein the server is configured to: receive information related to thedetermined differences the radio frequency beacon signal and theinformation related to the unique identifier of the mobile asset; andperform the location estimation in response to the data based on thedetermined values of the signal attribute.
 16. A light fixture-basedmobile asset detection system, comprising: a plurality of light fixturesdistributed in a service volume, wherein each light fixture comprises alight source for illuminating a portion of the service volume; aplurality of radio frequency-enabled nodes communicatively coupled in anetwork, wherein each radio frequency-enabled node is: coupled to amulti-element antenna array having multiple discrete antenna elementsconfigured to receive a signal emitted by a mobile asset within theservice volume, collocated with a respective light fixture of theplurality of light fixtures, and configured to: detect the mobile assetwithin a service volume based on receiving the signal emitted by amobile asset via each respective discrete antenna element of themulti-element antenna array, process the received signal to determine avalue related to an attribute of the received signal for each of therespective discrete antenna elements; generate information for a threedimensional location estimation based on the determined values relatedto the received signal attribute as received by the discrete antennaelements; and output a signal containing the information for threedimensional location estimation; and a fog gateway communicativelycoupled to the plurality of radio frequency-enabled nodes and theplurality of light fixtures, the fog gateway configured to control thelight fixtures and receive signals containing the information for threedimensional location estimation from the radio frequency-enabled nodes.17. The system of claim 16, wherein the information for threedimensional location estimation includes differences between therespective determined values related to the received signal between eachof the discrete antenna elements of the multi-element antenna array. 18.A light fixture, comprising: a general illumination light source; anantenna array having multiple discrete antenna elements; a wirelesstransceiver; a memory; a processor coupled to the transceiver and thememory; and program instructions stored in the memory, wherein executionof the program instructions configures the light fixture to: detect amobile asset within a service volume in response to receiving a signalemitted by the mobile asset, determine a value related to the emittedsignal as received via each of the multiple discrete antenna elements;and output data based on the determined value related to the emittedsignal as received via each of the multiple discrete antenna elements.19. The light fixture of claim 17, wherein the determined value for eachof the multiple discrete antenna elements includes: a signal phasevalue, an angle of arrival value, a received signal strength value, or atime delay of arrival value.
 20. The light fixture of claim 17, furthercomprises program instructions that further configure the light fixtureto: determine differences between the respective determined values forinclusion in the data.
 21. The light fixture of claim 17, wherein themultiple discrete antenna elements form a non-coplanar antenna array.